In continuous casting, hot molten metal flows directly or through a casting tube into a mould. In the mould the molten metal is cooled and a solidified, self-supporting surface layer is formed before the strand, the blank, leaves the mould. If inflowing molten metal is allowed to flow into the mould in an uncontrolled manner, it will penetrate, due to its impulse, deep down into the non-solidified portions of the strand. This renders difficult the separation of particles trapped in the molten metal, which adhere to the solidification front instead of being separated to the upper surface. In addition, the self-supporting surface layer is weakened, which increases the risk of molten metal breaking through the surface layer formed in the mould.
From, for example, Swedish patent SE 436 251, it is known to arrange one or several static or periodic low-frequency magnetic fields in the path of the molten metal to brake and split up the inflowing molten metal. The magnetic fields are generated by means of magnetic poles, permanent magnets or induction coils supplied with direct current, and are arranged to act across the inflowing molten metal. The magnetic poles are arranged close to two opposite mould walls. However, the solution according to the above does not take into account any changes and non-symmetry in the flow configuration. Changes and non-symmetry in the flow configuration occur not only because of changed mould dimensions and non-symmetrical location of the casting tubes, but also by, for example, erosion and clogging which disturbs the flow out of the casting tube.
A non-symmetrical flow configuration entails great problems with regard to quality and production engineering: For example, hot molten metal, with or without non-metallic particles, may penetrate without being braked deep down into the non-solidified parts of the strand with ensuing quality problems. The upward flows of hot molten metal towards the upper surface, the meniscus, may become too weak, resulting in a risk of the meniscus freezing. If, instead, the upward flows become too strong, wave formation arises on the upper surface as a result of the turbulence, which pulls down slag from the upper surface into the molten metal with ensuing quality problems.